Fluid Inclusion Characteristics And Genesis Of The Tungsten Mineralization In The Kunlun River Area,qinghai Province

The Kunlun River area of Qinghai is located in the Southern Kunlun accretionary complex belt of the East Kunlun orogenic belt.In recent years,many tungsten mineralizations represented by Tongjinshan and Erdaogou have been found in this area.On the basis of field geological investigation,combined with mineral identification and fluid inclusion analysis and other indoor research,the characteristics of geology and fluid inclusion of the two typical tungsten mineralizations in the area have been analyzed,mineralization types are determined,and the genesis of the mineralizations and metallization process are discussed.The ore body of Tongjinshan tungsten polymetallic mineralization is found in altered marble.Metallic minerals in the ore are mainly scheelite,followed by chalcopyrite,galena,stromeyerite,argentite,bornite and stannite,etc;non-metallic minerals are mainly quartz and tremolite,followed by serpentine and calcite,etc.The ore fabric is mainly idiomorphic-hypidiomorphic granular texture,metasomatic relict structure,sparsely disseminated structure.Mineralization is closely related to silicification and tremolitization.The mineralization can be divided into: I.Tremolitescheelite-quartz stage,II.quartz-sulfide-scheelite stage,?.calcite-talc stage,where I,?? are the main ore-forming stage.The main ore-forming stage mainly developed gas-liquid two-phase inclusion,and H₂O-CO₂ inclusion was rare.The homogenization temperature of fluid inclusion in stage II is medium high temperature,medium low salinity;in stage III,it is medium low temperature,medium low salinity.Fluid of these two stage all belongs to H₂O-NaCl-CH₄±CO₂ system.Tungsten ore body of Erdaogou consists of ore-containing quartz veins,produced in phyllite,slate.The metallic minerals in ore are mainly scheelite,and sulfide is rare.The ore fabric is mainly idiomorphic-hypidiomorphic granular texture,metasomatic relict texture,disseminated structure.Mineralization can be divided into: I.quartz-scheelite stage,II.sulfide-carbonate stage.The scheelite and quartz of main metallogenic stage mainly developed gas-liquid two-phase inclusion and CO₂-H₂ Oinclusion,and containing sub-mineral three-phase inclusion and melt inclusion were occasionally seen.Ore-forming fluid belongs to H₂O-Na Cl-CH₄-N2-CO₂ system which is high temperature,high-middle-low salinity coexistence,showing magmatic hydrothermal characteristics.And fluid immiscibility has occurred during mineralization.Tongjinshan tungsten polymetallic mineralization belongs to tungsten deposit of metasomatic rock type,and its formation is related to the percolation metasomatism of marble by medium high temperature ore-bearing fluid.The increase of Ca²⁺concentration and pH value and the decrease of temperature,results to crystal precipitation of scheelite.Erdaogou tungsten mineralization is tungsten deposit of magmatic hydrothermal vein type,its formation is related to high temperature ore-bearing thermal fluid filling.Fluid immiscibility has occurred during mineralization,which leads to CO₂ escapes from the fluid phase and the pH value increases,resulting in crystal precipitation of scheelite.